Think I'm pregnant but negative test

I've been trying for a baby for the past 2 months, so I had my contraceptive implant removed at the end of jan. I had a perfectly good period last month and this month I haven't came on. I'm now officially 6 days late on my period. I took a test yesterday and it said negative however I've had very sore boobs and nipples, very swollen and I've never had veiny breasts and the past few days they've got ridiculously veiny. Does anyone have any idea what could be going on? Reply would be amazing. Thank you.